Use correct position when setting pos_in_set for tabs.

chrome/browser/ui/views/tabs/tab_strip.cc

Index: chrome/browser/ui/views/tabs/tab_strip.cc
diff --git a/chrome/browser/ui/views/tabs/tab_strip.cc b/chrome/browser/ui/views/tabs/tab_strip.cc
index e22c45709fd4e6b4064187737033379e62305ec0..c57ee1cfc16e6806b244619f620f98a83efc651d 100644
--- a/chrome/browser/ui/views/tabs/tab_strip.cc
+++ b/chrome/browser/ui/views/tabs/tab_strip.cc
@@ -1343,8 +1343,12 @@ int TabStrip::GetBackgroundResourceId(bool* custom_image) const {
 
 void TabStrip::UpdateTabAccessibilityState(const Tab* tab,
                                            ui::AXNodeData* node_data) {
+  if (GetModelIndexOfTab(tab) < 0)

[sky, 2017/03/01 00:31:18]

Assign to local variable to avoid multiple calls.

+    return;
+
   node_data->AddIntAttribute(ui::AX_ATTR_SET_SIZE, tab_count());
-  node_data->AddIntAttribute(ui::AX_ATTR_POS_IN_SET, GetModelIndexOfTab(tab));
+  node_data->AddValidatedIntAttribute(ui::AX_ATTR_INDEX_IN_SET,
+                                      GetModelIndexOfTab(tab));
 }
 
 void TabStrip::MouseMovedOutOfHost() {